Universal Serial Bus (USB) connections are widely used today to enable connections between Personal Computers (PCs) and peripheral devices such as telephones, digital cameras, scanners, keyboards, mice and PDAs. The USB specification was developed by a group of companies including Compaq, Intel, Microsoft and NEC and the USB specification documents such as USB 1.1 and USB 2.0 are publicly available. The USB specification describes the bus attributes, protocol definition, transaction types, bus management and programming interface required to comply with the standard. Using this standard it is possible to provide a fast, bi-directional, isochronous, low-cost, dynamically attachable serial interface between a PC platform and one or more devices.
In many situations, devices to be connected to a PC or other similar platform using a USB connection are arranged to take in removable media (such as smart cards, bank cards, pre-payment cards, memory sticks, electronic purse cards or the like) and to output those media again when required. For example, it is known to provide a bank card reader connected to a PC via a USB connection as part of an automated teller machine (ATM) or other self-service machine. Typically a device driver is provided as software at the PC for communicating with the device over the USB connection which may be a card reader as in the example mentioned. It has been found that problems can arise with returning the removable media in situations where there is a loss of communication over the USB connection. This is particularly disadvantageous when the media is needed for use elsewhere, for example, if it provides an electronic purse or security details which are unavailable elsewhere.